Vinylidene chloride resin composition and container structures manufactured therefrom

ABSTRACT

A container structure for paste or high-viscosity liquid having stretch-oriented wall and improved shape-restitution property is manufactured from vinylidene chloride resin composition containing therein a particular polyester plasticizer such as a polyester produced by the reaction of succinic acid and ethylene glycol.

States atent VINYLIDENE CHLORIDE RESIN COMPOSITION AND CONTAINERSTRUCTURES MANUFACTURED THEREFROM 2 Claims, 1 Drawing Fig.

U.S. Cl 229/3.5 R, ISO/0.5, 260/316 Int. Cl B65d 1/00, C08f 45/38 Fieldof Search 260/316; 229/35 R References Cited UNITED STATES PATENTS Smallet a1. 6/1953 Smith 7/1966 Gorsich FORElGN PATENTS 5/ 1949 Great Britain10/ 1968 Great Britain Primary Examiner-Morris Liebman AssistantExaminer.l. H. Derrington Attorneywenderoth, Lind & Ponack ABSTRACT: Acontainer structure for paste or high-viscosity liquid havingstretch-oriented wall and improved shaperestitution property ismanufactured from vinylidene chloride resin composition containingtherein a particular polyester plasticizer such as a polyester producedby the reaction of succinic acid and ethylene glycol.

PATENTEI] DEC new 3.625409 INVENTORS NOBUYUKI HISAZUMI MASASHI ITO TAKAOICH II ATTORNEYS VINYLIDENE CHLORIDE RESIN COMPOSITION AND CONTAINERSTRUCTURES MANUFACTURED TI'IEREFROM BACKGROUND OF THE INVENTION Thisinvention relates to hollow container structures made of vinylidenechloride resin composition. More particularly, it relates to containerstructures of vinylidene chloride resins having a stretch-oriented wallof a thickness of from 0.1 to 1.2 mm., and an improved shape restitutionwhen deformed by external forces. The improvement in the shaperestitution is accomplished by adding high-molecular polyesterplasticizers to vinylidene chloride resin material to be used forforming container structures.

As a method for producing container structures made of copolymer resinscontaining vinylidene chloride as the principal constituent, there is,for example, a method according to our Japanese Pat. No. 521,771 (US.Ser. No. 531,399, British Pat. No. 1,129,626, German Pat. applicationNo. K 58,664, French Pat. No. 1,472,320, Italian Pat. No. 779,750). Acontainer structure obtained by this method has a wall which isstretch-oriented in a biaxial direction and has high strength and verylow oxygen permeability and vapor permeability. Accordingly, thecontainer structure is usually employed for packaging or bottling offood products such as ketchup and mayonnaise which readily deterioratedue to oxidation.

Such a container structure, however, is inferior to one made of apolyethylene in its shape restitution properly after deformation. Forexample, when pressure is removed from the container structure which hasbeen crushed under pressure during transportation, it is difficult forthe crushed container structure to return or be restituted to itsoriginal shape. Accordingly, when a number of the container structureare being filled with contents such as ketchup or mayonnaise, thequantity of the contents charged into the container structures is notconstant, and there occur frequent overflowing of the contents in spiteof the intention to charge a specific constant quantity of the contentsinto each container structure.

In general, there are two cases of shape restitution or returning of acontainer structure made of plastics and having a flexible wall whichhas once been crushed. The one is that the container wall immediatelyreturns to its original shape due to elasticity thereof when theexternal stress is removed, and the other is that the shape of thecontainer is returned to its original state due to the weight of thecontents at the time of its filling, which imparts pressure to the wallof the container.

When a liquid having a low viscosity such as water is charged into ahollow container structure having a thin and pliable wall, the fillingof the container structure with this liquid can be successfully carriedout with the original shape of the container due principally to theabove latter restitution.

n the other hand, when a paste having a high viscosity, such asmayonnaise, is charged into a container made of vinylidene chloride andhaving a medium thickness of from 0.1 to 1.2 mm. if the containerstructure is in a crushed or pressed state, the pressing force againstthe wall of the container due to gravity is influenced by the viscosityof the paste or liquid, whereby the shape restitution force is weakened,and, further, the speed of the restitution becomes very slow.Accordingly, it is necessary in this case that the shape of thecontainer be returned almost to its original state by its elasticityprior to filling with the contents and further that the shape bereturned completely to the original state by the filling of thecontainer.

Both of these two kinds of shape restitutions are influenced bytemperature, being particularly poor at low temperatures. Thisdisadvantage can be improved to some extent by the addition of a largequantity of antifreezing plasticizer to a vinylidene chloride resincomposition. However, while the shape restitution property at the timeof charging the contents into the container becomes progressivelyfavorable with increase in the quantity of the plasticizer to be addedto make the wall of the container pliable, excessive pliability givesrise to lowering in rigidity of the container structure at roomtemperature or higher whereby the shape-restituting property tends todeteriorate. Furthermore, when the quantity of an ordinary antifreezingplasticizer to be added to a vinylidene chloride resin composition isincreased, the gas permeability of the container structure deteriorates,whereby the characteristic features of vinylidene chloride resin arelost.

SUMMARY OF THE INVENTION It is the object of the present invention toprovide a container structure having a stretch-oriented wall of athickness of from 0.1 to 1.2 mm., and an improved shape-restitutionproperty, which is obtained from a vinylidene chloride resin compositioncontaining from 4 to 15 percent by weight of a polyester plasticizerhaving a mean molecular weight of from 500 to 4,000.

According to the present invention there is provided containerstructures each having a relatively high rigidity, excellentshape-restitution property due to elasticity and to internal pressure atthe time of filling with a certain content, and very low oxygenpermeability and being particularly useful for containers of liquid orpaste food products which are easily oxidized.

DETAILED DESCRIPTION OF THE INVENTION The polyester plasticizer to beadded to the raw material of the vinylidene chloride resin compositionof the present invention is a polymer which is produced from aliphaticdicarboxylic acid and polyol, is of a mean molecular weight of from 500to 4,000, and contains therein hydroxyl or carboxyl groups or thoseobtained by esterification of these end groups.

That is, polyesters produced from dicarboxylic acids each having analkyl group of a carbon content of l and diols each having an alkylgroup of a carbon content of m are represented by the following generalformulas (l), (2), and (3) depending on the ratios of the carboxylicacids and the polyols.

'acid, azelaic acid, sebacic acid, undecanedioic acid, and

dodecanedioic acid, or the isomers thereof, each of which has an alkylgroup containing from two to 10 carbon atoms.

Example of polyols suitable for producing the polyesters of the presentinvention are isomers of diols, each having from two to eight carbonatoms such as ethylene glycol, propanediol, butanediol, pentanediol,hexanediol, heptanediol, octanediol, and etc.

Furthermore, as monohydric alcohols and monocarboxylic acids foresterifying the end groups of the polymers, those having an alkyl groupcontaining from one to 18 carbon atoms are suitable.

A mean molecular weight of from 500 to 4,000 is suitable for thepolyester employed for the present invention. In the case of a polyesterplasticizer having a mean molecular weight of less than 500, the oxygenpenneability of the container structure will increase, if the polyesteris added to the vinylidene chloride resin composition by a quantitysufficient to obtain shape-restitution property of the containerstructure at TABLE Sample No 1 2 3 4 5 6 7 Resin, percent 94 93 80 84 8989 89 Paraplex 6-62. 5 l l l 1 l 5 DBS 1 0 0 0 6 Polyester 0 AB G-II ABG-Ii PA-A-l PA-A-ZO 0 10 15 i5 Oxygen permeability, cc.-cm./cin./mm.Hg/sec. at 30 C 4.5x10- 5.0)(10- 5.5x10- 7.0)(10- 6.0Xl0"" 5.5)(10'10.0X10'" Torsional rigidity:

k ./cm. at c i.a i0 i.2 10= i.0 10 0.9 i0 1.1)(10 155x10 i.0 i0=Kc./crn. at 0 C 4.5Xl0 2.8)(10 2.5)(10 2.0)(10 2.7Xl0 3.0X103 2.3)(10Shape restitution property at the time of filling water:

At (n=10) 20 (3., cc 185 190-200 200 200 200 200 200 At 0 0., cc l85185-195 100-200 200 200 190-200 200-200 i tit ti t i e t contain r atn=l0 room 122$?.Tiffiffiffiiflfii .l l a 4 4 4 3 2 ParapleitG-62=Epoxidized vegetable oil plasticizer (trade name). PAAl5=Polyadipioaeid-propanediol-aeetic ester; MW=1,500 (Made DBS=Dibutyl sebacate. byDaihachi Chemical 00.). Polyester AB GII=Polyadipicaeid-butanediol-aeetic ester; MW= PAA-20=Polyadipieacid-propanediol-acetic ester; MW=2.100 (Made 1.50 (M y A J- hypgihfighi q yhi hfl J; HJVWWV WW, 7 v I a low temperature, whereas inthe case of a polyester having a ally stretch-oriented wall. meanmolecular weight of more than 4,000, the shape-restitu- Each resultingcontainer structure which had a volumetric tion property of thecontainer structure will be poor. capacity of 200 cc. and a wallthickness of 0.2 mm. was sub- Furthennore, in the vinylidene chlorideresin composition jected t tests for oxygen permeability, torsionalrigidity, of the Present invention, 1655 than 5 Percent Of odi yingshape restitution when filling with water, and shape restitution agentssuch as plasticizers other than the polyester of the empty container.The results of these tests are indicated plasticizers, stabilizers, etc.may be added to the composition in the table. depending on thenecessity- The oxygen permeability of each structure was measured ASother modifying g innoxious ili r h as 4- according to ASTM-Dl434-58,the torsional rigidity was tert-butyl-salol and Tinuvin P may beemployed, and as agents measured according to ASTM-Dl043-5l, and therigidity serving as stabilizer-cum-plasticizer, epoxy stabilizers may bewa measured by the Clash-Berg method. also employed in the presentinvention. The total quantity of The shape restitution of the containerstructure when filled the polyester and modifying agent is within therange of from 3 with water was measured by leaving empty containerstructo 20 percent by weight. tures for about 1 hour at the temperaturesof 5 and 20 C., The raw material vinylidene chloride resin compositionof 3 5 respectively, charging into this container structure within 5 thepresent invention is a copolymer composed of from 70 to minutes 200 cc.of previously weighed water at a specific tem- 95 percent of vinylidenechloride and a monomer perature, and then obtaining the average quantityof the water copolymerizable with vinylidene chloride such as vinyl usedto fill the container structures, while taking into conchloride,acrylontrile, vinyl acetate, methyl metha r late, sideration the shaperestitution of the container structure itself methyl ryl e, ethy ene,propylene, maleic acid, fumaric and the shape restitution due to theinternal pressure of the acid, itaconic acid, and other ethylenederivatives. e d l a of the Water.

As circumstances require, less than 20 percent of other rub- AS theShape restitution of the p y cohialhel' structure ls also influenced bythe shape of the container structure itself, the degree of restitutionis as indicated in the table with numerals l, 2, 3 and 4. The degree isin practice determined by pressing the container structure underexternal force at room temperature to deform it, while observing andjudging the degree of restitution of the container structure when theexternal force is removed.

Since a factor influenced by the shape of the container structure isinvolved in the shape-restitution property of the empty containerstructure, in practice the container structure was crushed by anexternal force at room temperature to imberlike resins such asethylene-vinyl acetate copolymer, chlorinated polyethylene, and ABSresin may be admixed with the vinylidene chloride resin, in which casethe resin content of the composition is adjusted within a range of from80 to 97 percent by weight with respect to the total quantity of thecomposition.

The container structure of the present invention made of the vinylidenechloride resin composition to which the polyester plasticizer asmentioned above is added and mixed has a relatively high rigidity,excellent shape-restitution propeny due to own elasuclty and mtemalpressure at the part deformation thereto, and then the degree ofrestitution of of filling of the container and a very low oxygePermeability i 5 the container structure was observed and judged whenthe exwhich IS particularly useful for containing liquid or paste foodternal force was removed Pmdhcts which am easily oxldizable- In thetable, the numerical designations of the shape restitu- In order toindicate still more clearly the nature and utility on respectivejyindicate h f ll ing l of invention, the following specific example ofPlactice l. The case when the crushed container structure did notconstituting a preferred embodiment of the invention and 0 f lly returnwit i inal state. results are set forth, it being understood that thisexample is l 2 The case h h h d o t iner tr t re did presented asillustrative only, and that it is not intended to l recover li h l b h dr of the re titution was limit the scop of the in t quite unfavorablefor practical use.

3. The case in which the container structure under a slight EXAMPLEdeformation returned to its original state, but when it was A vinylidenechloride resin consisting of 80 percent by subjected to a largedeformation, its restitution was not weight of vinylidene chloride and20 percent by weight of adequate for pracucal 4. The case in which thecontainer structure exhibited sufficient shape restitution againstdeformation both large and small at least at the step of filling thecontainer structure vinyl chloride was employed to obtain mixturecompositions shown in the following table. Each mixture composition wasextruded from an extruder into a tubular shape and was immediatelycooled with water to obtain an amorphous-tubing ahquld' material. Eachamorphous tubing was stretched from 1.1 to in the above table, sampleNos. 2 through 6, inclusive, 2.5 times in its longitudinal direction.Each stretched tubing designate container structures of the presentinvention, and was clamped at both ends thereof in a metal mould toexpand sample Nos. 1 and 7 designate reference examples of the conanddraw so as to obtain a container structure having a biaxi- 7 tainerstructures which do not contain polyester plasticizers.

composition and having improved shape-restitution property, saidcontainer structure having a biaxially stretch-oriented wall of varyingthickness ranging from 0.1 to 1.2 mm., said material vinylidene chlorideresin composition composed primarily of a copolymer containing from 70to 95 percent vinylidene chloride and containing therein at least onepolyester plasticizer having a mean molecular weight of from 500 to4,000 and selected from the group consisting of compounds represented bythe following general formulas in an amount of 4 to 15 percent byweight:

2. A container structure as claimed in claim 1 in which said polyesterplasticizer is produced from at least one member selected from the groupconsisting of aliphatic dicarboxylic acids each having an alkylcontaining from two to 10 carbon atoms, preferably succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, undecanedioic acid, dodecanedioic acid, and isomersthereof and at least one member selected from the group consisting ofdiols each having from two to eight carbon atoms, preferably ethyleneglycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol,and octanediol.

2. A container structure as claimed in claim 1 in which said polyesterplasticizer is produced from at least one member selected from the groupconsisting of aliphatic dicarboxylic acids each having an alkylcontaining from two to 10 carbon atoms, preferably succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, undecanedioic acid, dodecanedioic acid, and isomersthereof and at least one member selected from the group consisting ofdiols each having from two to eight carbon atoms, preferably ethyleneglycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol,and octanediol.